Filled hard capsules in which the leakage or seepage of content is prevented have been desired as hard capsules filled with pharmaceuticals, health foods and other foods, cosmetics, agricultural chemicals, etc. Hard capsules filled with solids and thus free from liquid leakage problems may suffer deterioration of their oxygen- or water-susceptible contents if oxygen and water enter through the gap between the body and cap of the capsule. Therefore, a filled hard capsule in which the entry of oxygen and water through the gap is prevented has been desired.
Band seals have been used as a method to solve this problem. The band seal is a sealant (sealing agent) used to seal a fitting portion between the body and cap of a hard capsule after the contents are inserted in the capsule.
Polyethylene glycol (PEG), particularly a low-molecular-weight PEG with an average molecular weight of 200 to 600, has excellent solvent action and high absorptivity, and is therefore widely used as an excipient for drugs, quasi drugs, foods, etc. However, when PEG, which has a high moisture-absorptivity, is enclosed in a gelatin hard capsule that is weak under low-water-content conditions, the capsule film becomes fragile because of the reduced water content of the film. As a result, cracking is likely to occur over time.
Capsules formed of a water-soluble cellulose derivative, particularly hydroxypropyl methylcellulose (HPMC), as a film component have been proposed as non-gelatin hard capsules that can overcome the above-mentioned defects of gelatin hard capsules. However, it has been reported that when PEG is enclosed in an HPMC hard capsule that has high strength even under low-water-content conditions, PEG permeates and leaks out of the capsule film. Therefore, HPMC capsules are not suitable for use as hard capsules into which PEG or a composition comprising PEG is inserted.
To solve this problem, several hard capsules for use to contain PEG have been proposed. More specifically, hard capsules comprising at least one gelled polysaccharide selected from the group consisting of pullulan, hemicellulose, corn starch, carboxymethyl cellulose, and water-soluble salts thereof (Patent Document 1); hard capsules comprising pullulan gelled with a gelling agent (Patent Document 2); and hard capsules formed of a film comprising a polyvinyl alcohol as a base material (Patent Document 3) have been proposed as hard capsules suitable for use to contain PEG therein.
However, none of the above documents describe how to solve the problem of PEG leakage through the gap between the body and cap of the hard capsules.    Patent Document 1: Japanese Unexamined Patent Publication No. 2000-202003    Patent Document 2: Japanese Unexamined Patent Publication No. 2005-137935    Patent Document 3: Japanese, Unexamined Patent Publication No. 2001-170137